Not really hard, just boring. Attention span is just lost on it.
Weirdly enough I used to be able to do/stick to working on realism much easier as a kid, and I used to do it all the time. I was actually pretty exceptional at it for my age, lots of people were impressed and my skill ended up giving me a shitty 50% in art because 'IT WOULD NOT BE FAIR TO THE OTHER STUDENTS' if they gave me full marks because I could draw so well.
Then I discovered cartooning and anime and how much more fun that is to draw compared to realism. I just really enjoy the exaggeration and the stylistics looks off it, the art of making something look like something without every little detail and just simplistic or general lines was just... amazing to me. Now I get bored trying to do realistic stuff. Even semi-realistic is boring to me.